A number $x$ is rounded to 3 significant figures The result is 3.69 Write down the error interval for $x$.

Step 1 ：Find the range of values that would round to 3.69 when rounded to 3 significant figures: lower_bound = 3.685, upper_bound = 3.695

Step 2 ：The error interval for $x$ is \( \boxed{[3.685, 3.695)} \)